A Converged Cable Access Platform (CCAP) is an industry standard platform for transmitting video data and voice content. CCAP is led by CableLabs® of Sunnyvale, Calif. CCAP unifies the Converged Multiservice Access Platform (CMAP), managed by Comcast Corporation of Philadelphia, Pa., with the Converged Edge Services Access Router platform (CESAR), which is managed by Time Warner Cable, Inc. of New York, N.Y.
A virtual Converged Cable Access Platform (CCAP) is software that performs the functions of a hardware-based CCAP. The virtual CCAP may execute on hardware components that include a commercial off-the-shelf switch/router and one or more off-the-shelf computing servers. A commercial example of a virtual CCAP is CableOS™, available from Harmonic, Inc. of San Jose, Calif.
CableLabs has publicly issued a Remote PHY family of specifications known as the MHAv2 specifications (Modular Headend Architecture version 2). These specifications describe how a CCAP platform may be separated into two components, (1) a CCAP Core located at a cable headend, and (2) a Remote PHY node (RPN), which is typically located outdoors.
The CCAP Core may transmit multiple downstream channels to a plurality of RPNs. Each RPN, in turn, may transmit those downstream channels to a plurality of cable modems. Cable modems may send data, via an upstream channel, to the CCAP Core by way of the RPN.
Cable television often suffers from a problem where signals transmitted in the upstream direction from homes to the CCAP Core are interfered with by various noise sources. This type of interference noise is called ingress noise. Such noise sources include electric motors operated inside customers' homes (e.g., hair dryers and vacuum cleaners), switching regulators, and various Shortwave radio communications. Noise from electric motors and switching regulators is typically applied by the offending equipment to the power lines inside the homes, and the noise spreads to the cable television coaxial cable through common grounding of the cable television coaxial cable and the power lines. Noise from Shortwave radio communications is typically picked up by imperfect shielding of the various cables, adapters and customer equipment connected to the cable television coaxial cable. In the past, most ingress sources had a relatively short and temporary effect (e.g., when a hair dryer is used); however, some ingress sources have a continuous and longer-term nature (e.g., switching regulators inside LED light bulbs).
In recent years, a new type of ingress noise has proliferated. High power plant grow lights have become common, even in residential environments. These grow lights are driven by power supplies which are fed by line power. Often, these power supplies produce levels of electronic noise greater than those permitted by the Federal Communication Commission (FCC). These grow lights are often powered on for long periods each day. The ingress noise produced by these grow lights and their power supplies often is so strong that it drowns out and interferes with the regular signals transmitted from homes to the CCAP Core.
Typical CATV deployments have several tens or even several hundreds of homes connected to a single CATV node. The group of homes whose signals are combined into a single upstream receiver is typically called an upstream service group. Signals from an upstream service group are received at a node receiver or relayed over an optical link to a receiver in the headend/hub. Ingress noise originating from any one home in an upstream service group can interfere with the reception of transmissions from all homes in that upstream service group.
Ingress noise often occurs at the lower frequencies of the totality of the CATV usable frequency range. The noise amplitude of ingress noise also declines at higher frequencies. As a result, and due to the frequency allocation of the CATV spectrum where downstream signals are allocated at higher frequencies than upstream signals, ingress noise interferes more with upstream signals than downstream signals. Typically, the lower the frequency of an upstream signal, the more susceptible that upstream signal is to ingress noise.
The implementation of CATV nodes and other active devices in the upstream signal path from homes to the upstream receiver often has active devices for amplifying and processing the signals (e.g., RF amplifiers, laser transmitters, analog to digital converters, and so on). These devices are normally optimized such that signals at and around a small range of the expected signal level have the least amount of noise and distortion added by the active components. However, a strong ingress noise may cause a significant amount of distortion to be introduced by the active components, and can sometimes even completely saturate the signal path.